One of the major advances in recent years has been the increased use of optical communications systems for carrying very large quantities of information with low distortion and at low cost over great distances. Optical systems are also promising for such purposes as computing because of the inherently high speeds at which they can be operated. For these reasons, considerable development work has been done in making various photonics packages for use in such systems. Photonics generally refers to devices that share both electronic and optical attributes, such as lasers, which generate coherent light in response to an electronic signal, and photodetectors, which generate an electrical signal in response to light.
A fundamental problem in making a photonics package such as a laser source module is the alignment of a device such as the laser with an optical waveguide. As pointed out in the paper, "Glass Waveguides on Silicon for Hybrid Optical Packaging," C. H. Henry, G. E. Blonder, and R. F. Kazarinov, Journal of Lightwave Technology, Vol. 7, No. 10, October 1989, pp. 1530-1539, hereby incorporated herein by reference, monocrystalline silicon is a good choice of material for making such modules. The advantages of silicon derive basically from its extensive use in the integrated circuit technology; known processing techniques can be used for making in monocrystalline silicon various structures with various electrical properties and with a high degree of accuracy. For example, photolithographic masking and etching can routinely be used for producing device features with sub-micron tolerances. The paper describes a method for taking advantage of these attributes to make waveguides on the surface of silicon substrates that can be accurately aligned with other photonics elements mounted on the substrate.
In spite of continuing advances such as those represented by the Henry et al. paper, the problem of making low cost laser modules containing semiconductor lasers in accurate registration with output optical waveguides in a manner that permits their long term use has continued to be troublesome. Semiconductor lasers are typically made of a semiconductor compound material such as indium phosphide which is structually more fragile than silicon. Further, one must often provide a thermal path from the laser for appropriate heat sinking to avoid long term damage to the device. There is therefore a continuing need for production methods for making photonics modules that meet such diverse requirements and yet are amenable to mass production without requiring a high degree of operator skill.